People infected with HIV are at increased risk of cancer, due to AIDS-related immunosuppression, infections with other oncogenic viruses, and other exposures, such as tobacco and alcohol. This project inlcudes studies to examine cancer risk in HIV-infected persons and characterize risk factors for these infections. Likewise, recipients of solid organ transplants have an increased risk of cancer, due to immunosuppression induced by medications given to prevent organ rejection. This project includes epidemiological studies of cancer in transplant recipients. Two cancers of interest in these populations and others are non-Hodgkin lymphoma and lung cancer, both of which may be related to infections, inflammation, or immune dysfunction.